A collection vehicle's hydraulics are the Herculean muscles of a solid-waste fleet, but they demand constant care to stay in tiptop condition.

By David Downs

Hydraulics perform high-force functions upwards of hundreds of times a day, hundreds of days in a row—until something goes wrong. They may be powerful, but they're also sensitive, requiring scales of monitoring from the micron to the gallon, from the second to the season and beyond.

Without a tightly regimented routine of good-operating practices, preventative and scheduled maintenance, solid-waste specialists risk turning themselves into figurative firemen, says Marv Banowetz, a 20-year veteran of hydraulic systems and technical training director at Heil, a leading manufacturer of refuse trucks.

"If you don't do the elementary stuff every day, the PM, in six to nine months you'll be a firefighter. Every day something will break. That machine will dictate your day. You're a fireman at that point."

This month, MSW Management focuses on your fleet's muscles, the best way to maintain them and prevent flare-ups, as well as how some organizations around the country handle the task every day. Also, what does the future hold for quieter, stronger, safer, and more reliable systems?

Systems and Components

Collection vehicle hydraulics are based on the ages-old principle of force transmittance. Force applied at one point in a hydraulic system can be transmitted to another part of the system using an incompressible fluid. For the vast majority of collection vehicles, that fluid is an extremely debris-free petroleum product, usually with a rating of 15 microns or less. This oil is the blood of your hydraulic muscles, and tainted blood eventually dooms the system; but back to that in a second.

The force in a hydraulic system comes from a pump. For example, Heil's new, state-of-the-art Python fully automatic lift-arm system uses a pump capable of forcing 55 gal/min of oil into the hydraulic system. The buildup of this fluid downstream from the pump creates forces of upwards of 2,500 lb/in², producing well over 100,000 pounds of force, says Banowetz.

That force can be used to flip a 200-pound container bin into the hopper, compress waste, or eject the hopper's contents. However, the immense pressures created by the pump must be directed into the lift arm's many functions, which is where the "lift-control valve" comes in.

A lift-control valve directs system pressure into one of six circuits that can lift a container up and set it down, move the arm in and out, or grab and release the container.

Similarly, the "body-control valve" directs system pressure within the trash compactor, ejector, and tailgate. This is the section where fantastic system pressures truly come to bear, says Banowetz. Well over half a ton of pressure can be forced onto a cubic yard, sufficient to compact anything a driver would come across on a residential street.

Both sets of control valves have individual "port releases" to control how much of the total system pressure flows to the individual circuit. A port release will reduce total system pressure of 2,500 pounds per square inch to 1,000 pounds per square inch in the "grab" circuit; otherwise you'd crush a plastic container like a paper cup.

Lastly, all the prior systems direct force into different "cylinders," which do the actual pushing. The long, narrow cylinders contain a central piston. As a cylinder fills with pressurized fluid behind the piston, it pushes on the rod in the center of the cylinder. Pressure on the other side of the piston returns the rod to the home position. The biggest cylinders are the packer cylinders in the hoppers, says Banowetz. The Python systems uses two, 5.5-inch cylinders that fill up with 14 gallons of oil each in less than a minute, exerting upwards of 1,000 lb/yd³.

Between these major components, filters clean debris from the sensitive system with incredible speed and thoroughness, and are capable of filtering up to 85 gal/min of oil at a purity of 10 microns, Banowetz says.

The system would be nothing without hoses, which transmit force using specially engineered steel-braided rubber capable of withstanding up to 5,000 pounds per square inch. Seals and other smaller parts must also be able to withstand the immense pressures of the system. And lastly, an oil reservoir holds the immense amount of hot hydraulic fluid the system needs to keep running.

Controlling Contamination

The number-one issue in maintaining a hydraulic system, especially in a filthy environment like a garbage route, is contamination. Brad Poeth, a trainer with Eaton Fluid Power, estimates that some 70%–80% of all hydraulic failures can be attributed to fluid contamination.

"We often take an if-we-can't-see-it-it-can't-hurt-us approach to contamination. Unfortunately, the clearances in modern hydraulic components are so close that particles which are invisible to the naked eye can have a significant impact on the operation of hydraulic equipment," he says.

Poeth lists four sources of contamination: new oil tainted during myriad transfers from the factory to the repair shop; built-in contamination from new machinery; ingressed contamination from the environment; and the most dangerous form, generated contamination from within the system.

Poeth recommends filtering new oil before adding it, adding a "running-in" period for new equipment, using breather filters on reservoirs, sealing reservoir access plates, covering ports, repairing in a clean area, using cylinder rod seals, and using multiple filters.

Banowetz says changing your filters every three months and using the right specs can make a world of difference. Filter tolerances are dropping at Heil, says Banowetz. Before 2000, Heil was using 10-micron filters, but in 2000 Heil went to a 6-micron filtration system and in June the company went to a 5-micron system, "which is very impressive," he says.

Also, change the oil every 2,000 hours and consider taking oil samples, says Poeth. Analyze for particle levels, viscosity, acidity, water, and infrared scan every two months. It may be expensive, but it can extend the life of a vehicle considerably and even extend the life of oil.

It sounds simple, Banowetz says, but put the fill cap back in place, as well. "I've seen fill caps replaced with shop rags. The rag got sucked into the pump and you just blew hundreds of thousands of dollars in equipment," he says. Also, keep the oil reservoir roughly three-quarters full. Oil can expand up to 20% upon heating, and the lack of it will ingress air, causing rapid erosion of internal pump components.

Pay attention to defects in hardware, says Poeth. A pitted rod in a packer cylinder will ingress dirt, oil, and grime, and all system leaks mean something is getting in as well as out. There is no such thing as a tolerable leak.

Starting with a clean system and keeping it clean will fight generated contamination—the most dangerous type because the particles are "work-hardened," Poeth says.

Failure to maintain system cleanliness will lead to internal leakage and reduced efficiency, intermittent failures, and overheating, which can lead to hose breaks and catastrophic failures like 50-plus gallons of heated oil spewing into a public street, onto buildings, and onto the vehicle.

Effective Preventative Maintenance

Good operating practices also are part of preventative maintenance. Read the manual, Banowetz says, and train your drivers to do thorough pre- and post-trip inspections, regular greasing according to schedule, and a 10-cycle warm-up routine for drivers in cold climates, and to immediately respond to abnormalities like leaks, irregular noises, slowness, and speeding up. Trading drivers on trucks will also bring a fresh set of senses to a vehicle, and random supervisor inspections of vehicles can keep driver inspections honest.

Understanding the varying terrain of each truck can allow maintenance managers to adjust preventative maintenance schedules. For example, a truck negotiating a more hilly part of town will need brake work more often.

According to Banowetz, scheduled maintenance should be synonymous with preventative maintenance. Rigidly adhering to a set schedule of diagnostics, parts changes, and fluid changes prevents larger damage, and shirking to save money will cost organizations in the long run.

Trash trucks take a beating, so manufacturers suggest maintenance schedules may need to be shortened and amplified given the nature of the work. When it comes time to switch out parts, consider over-specifying certain trouble components like hoses. Some companies are over-specifying hoses by as much as 50%, Poeth says.

"Unfortunately, the real-world applications (especially on refuse haulers) can be far more severe and harsh than we would typically expect in an application. ... In our experience, we've found that spending more money on a higher-performing hose assembly can save money if the new hose assembly lasts long enough," says Nicole Skinner, Eaton technical communications generalist.

Rerouting, clamping, and shielding hoses during scheduled repair can also extend hose life by removing some of the rubbing that can shorten the life of the rubber.

Lastly, purchase compatible chassis and bodies with regard to spare-parts needs and existing equipment. It's hard to do scheduled repair when you don't have the new parts in stock and they take three days to get there, then require the dissembling of a major part of the chassis just to get to the part's location. Often, this requires a holistic approach that taps the know-how of mechanics combined with higher-level administrators who usually only see budget projections and cost-savings points.

System Profiles

The City of Glendale, CA, employs 17 staff members to maintain 46 collection vehicles among a 450-vehicle city fleet serving roughly 194,000 people. Mechanical maintenance administrator Dave Cole says the city largely uses Heil Rapid Rail sideloaders, augmented by 11 Pak-Mor frontloaders, one McNeilus front loader, four Pak-Mor rear loaders and two McNeilus rearloaders. Cole lacked specifics for hopper capacity or collection vehicle age, given the diversity of the fleet, but says most were less than six years old.

Drivers complete a 50-point pre- and post-trip inspection to double-check their gear, and the city emphasizes heavy preventative maintenance, Cole says.

"You have good PM and you don't get that many things in overhaul," he says.

Hydraulic systems remain finicky and unpredictable despite drivers' best efforts, he says. Full diagnostics, including total line checks, occur every 250 hours, with fluid changes every 1,000 hours.

"Usually a manufacturer will have a standard-duty and a severe-duty maintenance schedule. We go with severe duty," Cole says.

Hydraulic hoses are always blowing and cylinders are going, he says, despite drivers' best efforts to check fluid levels and change filters according to schedule. Cole says contamination isn't a problem as long as filters are changed on-time.

Glendale can rebuild blown cylinders, but outsources the operation because of cost efficiencies.

Marborg Industries in Santa Barbara, CA, uses six mechanics to field 25 vehicles for MSW, including commercial, residential, and recycling. In the interest of parts parity, Marborg manager Brian Borgatello says the private company tries to buy only Peterbilt chassis, most of them equipped with Heil 5000 bodies. Commercial work requires 40-yard Amrep frontloaders with three axles, he says.

Good operations practices aren't as important as in-shop maintenance, he says. Drivers must do pre-trip inspections by law, but pressure adjustments, greasing, and the like are handled in-shop. Drivers usually only talk to mechanics when there's a problem.

"If the cycle's running twice as fast, they aren't saying anything," says Borgatello.

Dealing with heat and contamination issues dominates preventative-maintenance operations. Multiple filters, a fluid specialist, and occasional fluid testing maintain hydraulic system cleanliness, but the heat issue isn't as easily solved, Borgatello says. Packing cycles run 400 to 500 times per day per vehicle, breaking down oil, seals, and hoses despite cooling systems that run on some trucks. "We just deal with it; we just repair them," he says.

Hoses are over-specified by as much as 50% by using steel-braided rubber made to handle up to 5,000 pounds per square inch, though the specs only call for 3,000 or 3,500 pounds per square inch. "It's way overkill, usually," he says.

Preventing ubiquitous hose ruptures also requires eliminating any and all rubbing in the system. Marborg mechanics make sure to reroute lines around sharp angles, or add clamping or shielding as necessary.

A 10-year-old software program orchestrates scheduled maintenance, spitting out daily maintenance operations that get combined with local experience regarding special routes. "Our Montecito front loader handles a hilly area and its brakes wear out about twice as fast, but the computer won't tell you that," Borgatello says.

The company also keeps deep stocks of supplies, and constantly updates them when the specs on a new piece of equipment changes. "We could build a garbage truck from scratch if we wanted to," Borgatello says. The company handles most of its own rebuilding, with the exception of cylinder re-chroming and line boring. Wear in the hopper is the biggest scheduled-maintenance issue, he says, as well as the rubber seals on the back doors, which prevent liquid from dripping out.

"Overall, the system's running pretty good, though," Borgatello says. "I think we got a really good hold on it."

Sunset Scavenger Company of San Francisco, CA, a privately held subsidiary of Norcal Waste Systems, serves the entire city of 800,000 with 375 employees, including 33 mechanics in two shops. More than 300 collection vehicles are on the road in any given year, according to maintenance manager Bob Bianchi.

Volvo chassis support most of the fleet, above which sit Lodal and Leach rearloader and semi-automatic sideloader bodies of anywhere from 18 to 30 cubic yards hefting up to 11 tons. Most of the fleet is probably less than nine years old, says Bianchi.

"I would say we've converted most of the fleet to semi-automatic sideloaders and we will be staying there for some time, with some full-auto in some areas," he says.

Leaking hoses and other hydraulics failures, along with terrain concerns, keep the fleet from going to full-automatic sideloaders, says Bianchi.

Sunset Scavenger uses an in-house trainer to drill drivers on good operating practices, including pre- and post-trip checks, which are augmented by random audit inspections by supervisors. Onboard programmable logic controllers mitigate abuse by drivers, who cannot readjust pressures to get a quicker cycle.

Preventative maintenance includes regular greasing by mechanics, an extremely rigid diagnostic schedule, as well as fluid and filter changes according to a five-year-old computerized schedule, Bianchi says. Hoses are over-specified by about 25%, he says, and Sunset Scavenger works with factories on rerouting hoses around rub points.

The company also sends maintenance trucks into the field to deal with such smaller repairs as a broken wire or a blown hose.

"Even with good operating practices and computerized PM, the nature of the business is such that wear and tear remains high, especially on hydraulics," he says. The best you can do is stay aware.

"The trucks basically run on many lines of hydraulics which have a tendency to start to leak, and usually if you catch it ahead of time you can avoid a major hydraulic line breaking," he says.

Scheduled maintenance for so many vehicles requires close relationships with manufacturers and a constant supply of intellectual capita, says Bianchi.

"Like anything else in the refuse industry, they don't have a lot of specialized courses. It's very difficult. You get a piece of equipment, you have it for a little while and start to learn more and more."

Sunset Scavenger is capable of handling its own rebuilding, but farms out cylinders because of cost.

The City of Siloam Springs, AR, is a tiny operation serving nearly 14,000 residences with three mechanics working on about 244 vehicles in the city, six of which handle waste and recycling. Garage maintenance manager Don Mullikin says the solid-waste fleet's chassis are all Ford, with four unspecified rearloader bodies and two Pak-Mor sideloaders. Capacity ranges from 15 to 25 cubic yards and ages range from four to 10 years.

Mullikin says bad operating practices cause truck problems every day. Drivers are supposed to grease the vehicles weekly and go easy on the hydraulics, but there's no penalty for shirking duties.

"It seems like we're always having hoses break because they are trying to shove more in there than they should."

Preventative maintenance is dubious affair, with Mullikin using an Excel spreadsheet to track needed changes and diagnostics. The city has attempted to switch to FleetWise's maintenance management software program for the past two years, but human error continues to ground it.

"I didn't think there was lot wrong with the old system, except Excel couldn't kick out repairs based on mileage. With the new system, not everyone's putting in the right mileage, so it's not working," he says.

Mullikin usually doesn't bother with fluid changes on any regular basis, because the frequency of blown hoses necessitates new batches of oil regularly, he says. Filters get changed anywhere from every 500 to 1,000 hours. Contamination isn't an issue unless it's moisture, he says, which occasionally enters the system.

The diversity of vehicle bodies in Siloam Springs's fleet often means delays between problems and the arrival of necessary parts. Siloam Springs does zero rebuilds, opting to replace broken pumps and outsource cylinder repairs to a firm in a different town. Also, confusion over part numbers is adding days to service timelines.

"We'll order parts from Ford and get the wrong one. We'll give them the [vehicle identification] number, but there's actually two products for that one [vehicle identification] number. It happens like that all the time and I have to send it back and wait for the right one to come in."

"We keep some things in stock, but can't keep it all and there's no way to know what you'll need," he says. "I'd like to see them stay with pretty much one brand. We deal with Ford, Mack, or Chevy and it makes it kind of hard to know all of them. But it's out of my hands."

The Future

Smarter, quieter, more reliable equipment has improved by leaps and bounds over the decades, Banowetz says, but the next step might require mechanic pay raises to compensate for the specialized electronics in the future collection vehicles.

Multiplexed systems like those used in Europe will eliminate multiple wires in exchange for one central wire that runs the length of the system, stopping off at nodes for a certain function. Such multiplexed systems promise foolproof collection vehicles that prevent drivers from over-speeding the system or otherwise damaging hydraulics with their own strength.

"We pretty much limit what they can do unless they can actually rewrite the software," Banowetz says.

Programmable logic controls are already rolling out with the new Python arm to limit the banging accompanied by reaching the top of the arm's lifting arc. Any sort of banging causes sheer stress on metals and will wear it out over time.

Proximity switches will prevent drivers from driving off with the ejector extended, which can bend the chrome rods in the cylinders.

Tighter filtration specs like those rolling out of Heil in 2004 mean less contamination and the resulting problems, Banowetz says. Synthetic fluids are being deployed in Europe, but they're expensive, and with the frequent leaks on trash trucks, you're talking accidentally dumping barrels of costly fluid (and money) onto public streets.

Quietness remains an issue in urban areas, and the advance of operate-at-idle systems has offered the latest innovation. Until recently, drivers had to rev the huge truck engines to get more power to the pump, causing the stereotypical roar of a trash truck in action. Newer trucks operate at idle as systems utilize a huge pump that doesn't need the engine revolutions per minute to create the force, but it's tricky, says Banowetz. The torque needed for the pump can kill an engine.

"We use electronic pressure sensors to shut off pumps and reduce torque before the engine will stall," he says.

Packing pressures aren't likely going any higher, Banowetz says, due to tonnage restrictions on the trucks, but cycle times on automatic arms have dropped dramatically to 6 seconds for the Python, which has a 9-foot reach. Using full system pressure, a flinging garbage container can now knock someone out who doesn't maintain clearance.

The biggest innovation, Banowetz says, may be wages.

"Typically in our industry, we don't get the cream of the crop. I believe that in order for us to maintain qualified technicians in the future you're going to start to see a salary spread meant to keep people working on dirty smelly, extremely complicated equipment."

Conclusion

Hydraulics have revolutionized solid-waste pickup, but the complexity of their systems is a revolution in itself. Modern equipment requires the tender loving care and exact specifications one might find on a space shuttle—one that has to fly daily through a world of filth.

Keeping such systems clean requires constant vigilance and an eye for the larger picture, where minute lapses in preventative maintenance can add up to costs that are orders of magnitude greater than the originally prescribed care. Companies across the nation must contend with tight budgets while trying to treat their machines the best, and those that fail become firemen in no time.

The future holds more exacting standards and even more technology, with the possibility of refuse systems as advanced as the world that generates the trash in the first place.

Journalist David Downs is based in San Francisco, CA.

MSW - September/October 2004